• Oxygen transmissibility, thickness, and water content were measured for three types of collagen shields: six of each type designed to dissolve in 12, 24, and 72 hours. Oxygen transmissibility was measured by a polarographic method at 35°C and was found to be 17.9, 17.3, and 23.8 × 10-9 cm mL O2/s mL mm Hg, respectively. Thicknesses were measured with an electronic gauge, and the central thicknesses of the 12-hour shields were found to be significantly greater (mean thickness, 0.19 mm) than the central thicknesses of the other two types (0.15 mm each). Water content, as measured by a hand refractometer, was found to be about 63% for all three types of shields, and no statistically significant differences were found. These measurements indicate that collagen shields behave like 63% water-content hydrogel contact lenses (oxygen permeability estimated at 27 × 10-11 cm2 mL O2/s mL mm Hg) with regard to oxygen transmission.
Weissman BA, Lee DA. Oxygen Transmissibility, Thickness, and Water Content of Three Types of Collagen Shields. Arch Ophthalmol. 1988;106(12):1706-1708. doi:10.1001/archopht.1988.01060140878032